Electric arc extinguishing apparatus



Dea 22. 1942. E. w. seems 2,3o6,2o4

ELECTRIC ARC EXTINGUISHING APPARATUS Filed Oct. 2,' 1940 2 Sheet's-Sheet 1 Fig. 2.

Inventor': Eugene Boehne,

1 N & 47

His Attorng.

Dec. 22, 1942. w goa 2306204 ELECTRIC ARC EX TINGUISHING APPARATUS Filed Oct. 2, 1940 2 Sheets-Sheet 2 Inventor':

Eugene W Boehne.

Patented Dec. 22, 1942 UNITED STATES PATENT OFFICE ELECTBIC ABC EXTNGUISHING APPARATUS Eugene W. Bochne, Drexel Hill, Pa., assinor to General Electric Company. a corporatlcn of New York Application October Z, 1940. Serial No. 859.363

5 Claims. (CI. 200-144) l inte the are chute and is stretched and lo el ns'ated,thereby increasinzthe are r'esistance.- until-thencin Hcwever, in the: casco! heavy currents-. this method alone may be p th .withinathechute b meansotspacedinteh nninwalls'fot -this passage also: exact meet i'rom thercustreamsztherehyatufler a'increasinz the resistaneentsthe mix-ap c ::1-

tur::- deflning a tortuous "arc 'passage in'which both 'the configuratio'n oi the'passagewey and 30 the magnetic rforces of' thearc current therein are so related as to provide more eirective heat transfer between the arc stream andthe pes-` sage side' wails than heretoi'ore attainable.

In previous are chutesot -this`-genera1 type the interleaving flns were evenly' spaced and made as plates-oi unirorm thickness proiecting perpendiculariyjrom the sidewails; :Cons' eqientlr"the' serpentine -arc passageway 'deflned -by these 1n- W terleaving "flns' comprises aseries oi transver'se -iu ections parailel to and equidistait rrom adj ecentsections doined byshortflongitudinal end secticns detlned by'the spacing between the-in axtreme edges 'and the "chute'side valle. 'such a" :onngu'r'ation is' sliown, *-ior -exhnple; in '-Patent'4 No. 2393513, issued August' 1821942. to L J;

Linde ior Eiectric air-:'circuit'-breaker.""

In .serpentine -arc paths` of this type. 'active magnetie forces inherent in the arc -current tending .to urge the arc' into closer reletionshlp U with the chute wall structure exist only at the oop tip ends and act outwardly toward the chute walls. That is. the mngnetic forces oi' the arc :uz-rent in the transverse sections, because of the A principalobject :o't myinvention 'is the. prcvision ctinprovedarcexting'uishing apparatus? oi' the atoresaid type comprising are chute' strucanother. tend tobe neutralized so that the are ,is maintained substantialiy centrally o! the transverse passages without necessarily-being in contact with either side weil. This obviously limits and retards the ere cooling action.

In accordance with my !mention theinherent mmetic' forces oi', thearc current-.are most e!- tectiveiy utilized to promote `etersireheat transfer by providing in an improved are chute s. -passagewax !or the nrc in which-adJecent transvcrse pcrtions either do not 'lie paranel to 'each other or arein irres'ularl m d re shim t'nerehya .stateot 'unhalanced masnetic interacticn is -established sbstantially-:aiong the whole'iength o! magne'ticzicr'ces :actively tend: toglisplacethe arc :sideways tromacentral pcsitionri thei pescage intmgreater heat -transter. reiationshipavith .tional view partly-in section ot 'the essential parte of 'an air -circuit breaker invention; !1302 'is na: sectional 'along the iine zcf Fig. 1,"Flg. alsfasectional eniarge'd viewtakeniaiong the`line tl ot Fgl 1, Figrgi is a partly diagrammatic view'iilustrating principies underlying the' present invention. Fig. 5 is anenlarged seetlonal view genrally* similar to that of Fig. a l 'i'fi'is a similar sectional view ot -another form or-are chute 'stru'ctu're embodying inyinventicn; Flgflis a end ectional view i ancther u'odiflcaticn' oi *my* inventicn. and Fle'. 815 a' imilar end'sectionaiIview-ofancther torm my'invention may-assume. I

The "air "circuit brenker illustrated bfm. `1 is 'of the magnetic'blowout type manun-ami i'or example in a form that is particularljfdjptable tor centrai etaticns'hnd sub-station whe'rein' the circuit `-breaker unit can be licdiidisonected with tc-the stationarvircuit. *This form of circuitbreaker* is generali? iiorprated in metal-'clad structure i'or v'ertical -movement ther-ein. However. since this feature forms no part of the present invention. a complete disclosure t'hereoi is omitted in the interest oi' clear-nese.

Reterring speciflcally to the circuit breaker includlng the contact structure and the are extlnatter lying parailel to and equidistant from one 55 guishing means, the relatively movable contact structure ccmprises a fixed contact i and a movable contact 2 that is pivotally mounted at 3 on one of the circuit breaker studs' and is operated by means o! a reciprocaily movable rod l. The Operating rod is suitablyconnected to an actuating mechanism (not shown) tor Operating the movable contact between closed and open circuit position. The contacts I and 2 are electrically connected to the lower ends o! the breaker conductor studs 5 and 8 respectively which also serve as the terminals oi the breaker unit. Accordingly, when the breaker is connected in series in a power circult and the contacts l and I are separated, an arc may form across the gap indicated.

For the purpose of interrupting this power arc. an arc extirguishing structure generally indicated at 'i is mounted with respect to the contact structure so as directly to receive the power arc which is under the influence of the magnetic blowout il'elds produced by the coils I and I. In the arrangement so tar described. the arc extinguishing structure is similar to a conventional are chute wherein the are is tormed at a narrow entrance part oi the chute and is rapidly extended in the form oi' a loop through the chute.

Rei'erring more particularly to Fig. 2, the arc exting'uishing structure comprlses closely spaced side wals o and li composed oi' are resisting material, such as i'or example an asbestos compound or a suitable arc resisting ceramic material( Each side wall oi the chute at its inner side racing the other wall is provided with a plurality ot parallei 'ib-like flns or ridges ll' and il' respectively. The ridges li' and li' are preferably integral with the side walla oi' the chute which are Joined and suitably clamped together e at the ends I! and II. The length and spacing of the ridges ill' and il' are such that when the side walls lil and II are clamped together, the ridges are interleaved with respect to each other. i. e., in staggered relation, so as to form a zigzag passage Il having alternating salicnts into which the arc is driven at the entrance II or the are chute 1.

As clearly shown by Fig. l. which illustrates but halt the extinguishing structure in detail, namely the side wall Il, the ridges extend paralle] in spaced relation in a direction transverse to the direction ot the movement of the arc as it passes from the entrance IS into the chute. These ridges, as will be explained later in detail. are formed so that unbalanced magnetic interaction is established with respect to the adjacent sections of the arc to force a maximum amount of the total arc length against the side walls of the tortuous passage il. In Fig. 2,' the ridges are shown in cross section as broader at the base. gradually tapering toward the tips thereby deflning a zigzag passage generally similar in form to that shown by Fig. 5.

It will be understand that my invention is not limited to the specific i'orm ot chute illustrated by Fig. 1 and that by way oi' example the longitudinally straight ridges, instead of being arranged in straight parallel relation as shown, may follow concentric curvilinear paths or paths radiating from the chute entrancc.

As the are i'ormed between the scparating contacts is driven by the magnetic blowout field into the entrance passage li oi the arc emnmlshing structure. there is comparatively little transverse deflection of the arc stream during this Initial movement due to the !act that the ridges n' and li' are tapered along the longitudinal azis &806304 !rom the exhaust end of the chute toward the arc entrance at II. This arrangement is clearly illustrated by Fig. 3. As the arc is driven into the zigzag space deflned by the interleaving ridges, the cross section ot the arc is reduced as the are more and more assumes a serpentinc form. I! a heavy current arc is to be interrupted. interruption may not occur until the arc has been moved weil into the chute.

Up to the point oi' interruption. the blowout field continues to move the arc outward through the arc passage. thereby progressively lengthening the path ot the arc as the amplitude oi the zima path becomes greater. The arc is thereby greatly lengthened and attenuated concurrent with very eii'ective cooling due both to the large cooling surfaces ot the ridges as the arc approaches the exhaust' part o! the chute and to my improved method oi establishing unbalanced magnetic forces of the arc current for obtaining a greater degree oi intimate contact between the arc stream and the effective cooling sui-faces oi the chute.

The switch contacts and the magnetic blowout structures can assume any preierred form and comprise no part oi the present invention so that a brief description will be sumcient. The magnetic blowout coils I are electricaly connected to the conductor stud 5 and to the are runner 8' so that the arc current traverses the blowout coils in a manner well known in the art. Normally, the current is can-led in the closed circuit position of the breaker by the spring biased contact I', the current being shmted to the arcing contact at I upon opening o! the breaker. As the arc is drawn by the movable contact I. it is transrer-ed to the arc runner 9' when it passes the position indicated by Fig. 1 so that the blowout coil O. which is electrically connected as indicated to the conductor stud i is now connected in series with the arc current. Accordingly, the blowout coils are energized by the arccurrent to lnfluence'the are in a well known manner, i. e., to project the arc into the chute in an ever expanding loop. For the purpose of utilising the blowout field to the greatest extent, iron pole pieces are s'ecured along the outer sides oi the arc chute. o

For the purpose oi' suppressing and conflning within the arc chute exceptionally heavy overload or short circuit currents that may be sometimes encountered. an additional arc suppressing unit it is provided at the exhaust end of the arc chute. This unit comprises a compact gridlike structure which also !realy vents arc cases generated within the chute. This arc suppressor unit iorms no part oi' the present invention and is speciflcally disclosed and is claimed in the mnde patent supra. A detailcd description of this unit is unnecessary for a complete understanding of the present invention. lt being sumcient to state that the exhaust end o! the zigzag arc passage opens into the grld-like suppressor unit tor venting the chute gases.

The underlying principles oi' operation of my improved are interrupting means tor establishing unbalanocd magnetic interaction. together with various forms my invention may assume. will now be explained. It has been stated that the resistance oi' the arc stream is progresaively increased concurrent with lcngthening and attenuating thereoi' as the arc is forced into a more and more tortuous path in the chute passage il. This increase in arc stream resistance causes decrease oi' the arc current and also improvement oi the power !actor of the circuit. all o! which serve to aid interruption.

It can be stated that during lnterruptlon, the arc energy increases up to a point where the arc resistance in ohms equals the external circuit impedance in ohms. At this stage, maximum energy liberation occurs. The phase angle hasshitted to 45' and the current Is 703% ol its value at nero power factor. With the continued movement o! the arc into cooler regione of the chute. the are resistance is further increased and a state soon edsts in which the chute walls are capable of absorbing the arc heat energy at a rate exceeding that o! the are beat liberation. This state having been reached the arc may then' be described as being on the "downhill side" toward interruption. since the present invention is primarily concerned with alternating current circuit breakers. this are phenomena is particularly advantageous since interruption generalb; occurs at the next current zero.

In the above described interruptins process involving progresslve increase oi' the arc stream resistance. the cooling or beat-transfer action plays the most important part and lt is therei'ore essential that for most eii'ective interruption the' arc be forced into intimate heat transfer relation with the cooling sirtaces of the chute. I accomplish this by so des z lng the tortuous are path that unequal magnetic forces Interact between adiacent portions of the are stream so that extensive sections 'ot .the are are biased by mas netic forces so as to hug' the conflnin'g wall: oi passage. 'fhisfintimate contact between the are stream chute structure ob'viously bring; about a much'higherrate oi' heat transfer rrom "thearc streamj the case: wherethearc nisjen-een r'c ess ze.

interrupting method hbqve described.- 'An 'else-*- trio' a is sublect 'toall the'` laws o1' magnetic ;torces 'acting on conductors.-

Thgu d menta lation o! the interacting force v i J :a w

where:

K=Numerlca1 constant I= Current in one conductor :Current in other conductor d=Distance between them A F=Force acting on'each conductor As !s well known, this force acts through all non masnetic materials.

Reference is now made to F'ig. 4 which diagrammatically illustrates a single current carrying conductor A- B-C folded upon itself to form three parallel conductors positioned between rlgid insuiating walls w' and W. Let it be as'- sumed that the initial spacing between the paral lei conductors A and B is d and that between the conductors B and Cis d: and that by way of example d: is appreciablyreater than d. 'The insulatingjiall:

jabsence 'fth wall W until the present illustratlon. the co conductor C. which is also restrained by the ad- Jacent rigid wall w can be similarly expressed as:

It therefore !allows that this relation will be satisfled only when d=d. i. e. when the spaclng between the conductors A-B--C is equal and uniform.

Now let it be assumed that a cool insulating rigid surface (not shown) is positioned between the conductors B and C to prevent the conductor B from movingto its'position of magnetic equilibrium. Iij'now, we further assume that the conductor Bis a portion o! 'the arc stream. it will be apparent that the insulatin'g wall below the conductor B would' now be in intimate good heat transier relation with the are stream. i. e., the magn'etic toi-ces between the conductors A and B would cause the arc portion B to lay flat against and bug restraininglinsul ating wall; since this force rcacts equally in opposlte directions, it also follow: the conductor o'r are portion A also would' betorced nat against the insulating A similar' analysis will that if-the conduetors B and C are both *'h;eld"`ri8id,con-

doctor *A forced tem npward in' the dr. Howevenin uctor o' are pormetricall y `'with' respect `to- `adiacent portions thereo! instead of symmetrlcally', the are will be forced by the reacting ma netq forces more intimately' against' the adjacent passage walls deflning cooling surfaces thereby extracting heat from the arc'stream at a higher'rateand greatly facilitating arc internption.

Fig. 5, which is merely an enlarged and somewhat exaggerated view of the arcpassase structure shown by Fig. 2, illustrates how the above principles are applid in a prapticaliorm. The ridges. ill' 'and ll' of the chute side'walls' lll and I I respectivly arenested in 'slightly spaced interieavin g `relatiori to form the'tortuous zigzag are path IL As indicated by Fig; 3, thisis representative of the iorm' of the arc passage throughout the greater part 'of the chute toward the elaust' 4` asoasos those portions of the are at the opposite sides of the ridges li' indicated by the spacing d will be flattened against the opposite walls of the ridges III' by reason of the resultant magnetic forces due to the inequaiity between the spacing d and da. The same is' obviously true oi the arc at the opposite side of the center line, i. e., the corresponding arc portions at that side will be flattened against the walls of the chute ridges ll'. The only points of magnetic equilibrium are along the center line itself. so it follows that the greater part of the arc stream is subiected to the more intensive cooling action above described.

Other important advantageous !actors are involved in this particular zigzag conflguration to estabiish the latter as the preferred embodiment of my invention. Referring again to Flg. 5, lt has been shown and will now be evident that the unbalanced magnetic forces serve to drive the arc away from thegtips of the pyramidal cross-sec-` tioned rldges into the beses of the adJacent ridges so that the arc hoat is directed into the sections of greatest mass in the chute structure fo'r instantaneous heatabsorption and toward the chute side walls where the acquired heat is readily dissipated. In addltion, this increasing cross-section lspartlcularly effective for rapidly draining the heat from the body of the ridges and also from the comparatively narrow tips where burning otherwise would be more pronounced, so that the chute structure is rendered longer-lived.

By way of example, it will therefore be evident in comparing' the prior type parallel-side ridge to my improved tapered rldge. the cross-sectional area and depth of the two ridges being equal. that the tapered form is superior magneticany. physically and mechanically.

described. each ridge at its outer end is provided with an enlarged portion having a bulbous crosssectional area as iilustrated so as to establish a spacing d: for the corresponding loop of the arc. Each ridge near its base where it is united to the correspondlng chute wall on the other hand tapers to a narrow necl: so as to estabiish a comparatively small spacing d for the reacting portions oi' the adjacent are' logs. It will therefore be seen, referring speciiicaly to the arc at the left of the center line lndicated, that the strong and predominant magnetic forces reactine through the space d cause the -arc portions at the opposite sides of the narrow nec! to flatten against and hug the passage walls defined by the bulbous parts of the ridges zi'. The arc stream is thereby cooled at a high rate by the forced contact with the passage walla.

This effective cooling oflthe arc also takes place in a similar manner at the right side 'of the center line for the same reasons and since the only main points of magnetic equilibrium are I along the center line as in the case of Flg. 5, it i will be observed that the greater part of the The essential form of the are passage above described is deflned by altemating caliente, one salient having a transverse dimension (i. e., parallelto the= center line) throughout an appreciable part' thereof (i. e.. between the tip and center line) that is appreciably .less than the aligned transverse dimension of the adiacent alternating salient (i. e.`-. the dimension d as compared withdsi sei that an unbalanced state is thereby established between the magnetic forces of the arc current for causing the are portions at opposite sides of said lesser transverse dimension (i. e.`, the dimension d) to be forced in opposite directions against the insulating walls of the chute passage in heat transfer relation thereto.

By way oi example. I havefound from comparative testa of two arc chutes identical in size. construction and material except that one was of the conventional symmetrical type and the other designed for unbalanced magnetlc interation in accordance with 'my invention that my improved chute was capable of inte'rupting a maximum current 1.8 times that of the conventional symmetrical chute even though the circuit voltage in the case of my chute was 1.17 times greater.

In the form oi' my invention` shown by Fig. 6. which illustrates the exhaust 'end of the chute as in the case of Fig. 2, the opposing chute walls !II and !i are provided with spaced interlocking and intel-leaving ridges 20' and !I respectively. These ridges form between each other and the cooperating chute walls an arc passage 22 of somewhat exaggerated serpentine shane and extend substantially parallel through the chute as in the case of Figs. 1 and 3.

For the purpose of providing magnetic unbaiance for aflecting the arc in the manner above are stream is postlvely and effectively "cooled by the heat transfer relation establishedwith the chute passage walla. l

The modification illustrated by Fig. "l, which shows the exhaust end of the chute as in the case of Figs. 2 and a is so closely related to the diagrammatlc arrangement shown by Fig. 4' that the operation is believed to be clear without detaiied description. Thechute walls and. :I are provided with interleaving flns or ribs 30' and Il' respectively. theflns n' being narrow and appreciably spaced and the flns sl' being comparatively thlck and closely spaced to form the unsymmetricai are' passage 32. sincethis passage closely simulates the form of` the conductorof Fig. 4. further description is believed to be unnecessary other than to state that the arc portions at the opposite sldes of each narrow fln 30' are forced in opposite directions by the resultant magnetic 'forces into good heat transfer' relation with the walla of the compare.- tively thick ribs si'.

In the modiiicatlonshown'by mg; a, dl ssym.

metry is acconplished by appreciable variations in the length and positionlng of the cooperating flns. In this lnstance, the chute side walls ill and II are each provided with flns, some of which are miei-leaving and others spaced in alignment'. The finan' of the chute wall lil are in part unequaliy spaced and receive certain flns li' of the chute wall ll in interlcaving relation. However, other flns of .the wall ll ndicated at Il" are shown as of limited or "stub" length and in spaced alignment with the cooperating flns w. 'It will be apparent that in this design the arc is both lengthened by the interleaving arrangement and also attenuated at the gaps between the fins lil' and ll" as well as being intensively cooled at the comparatlvcly narrow loops where the aus. 40' and ll' interleave. Further description of arc cooling action is believed to b'e unnecessary in view of the simiiarity between the arc' paths of Flg. 'l and Flg. 8.

It should be understood that my inventlon is not limited to specific details of constructlon and arrangement thereof heroin illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of my lnvention.

What I claim as new and desire to secure *by Letters Patent of the United states is:

1. Electric arc extinguishing apparatus comprising an insulating arc chute into which the interrupting arc is directed having side walls disposed in closely spaced relation so as to form a narrow eiongated arc space, said walls on the sides iacing each other having projecting therefrom elongated ridges extending generaiiy in the direction of arc movement, ridges of one wall being spaced and interleaved with respect to ridges oi! the other wall so that together they form a restricted tortuous arc extinguishing passage of zigzag form extending through said chute and having a cross section characterized by alternating salients, interieaving ridges of said walls having a height at least equal to or greater than the width of the corresponding ridgerbase so that said ridges form deep salients in the opposite wall structure, the transverse dimension of one salient throughout a part .of its height being materiaily less than the aligned transverse dimension o! the adjacent alternating saiient so that a material degree oi' magnetic unbalance is thereby established between the magnetic forces of the arc current along the opposite sides of said salients, said magnetic unbaiance causing the arc portions at opposite sides of said lesser transverse dimension to be iorcibly urged in opposite directions against the insulating wall of the chute passage in heat transfer reiation thereto for materiaiiy cooling the arc stream.

2. Electric arc extinguishing apparatus comprising an insulating arc chute intoewhich the interrupting arc is directed having side walls disposed in clcsely spaced relation so as to form a narrow elongated arc space, said walls on the sides facing each other having projecting thereirom ridges extending generally throughout said chute in the direction of arc movement, ridges of one wall being spaced in interleaving position with respect to ridges of the other wall to form a restricted tortuous arc extinguishing passage characterized by alternating salients, interleaving ridges o! said walls having a height greater than the width of the corresponding ridge base so that said ridges form deep saiients in the opposite wall structure, the cross sectional thickness o! each ridge decreasing rrom the base thereot where it joins the corresponding chute wall to the tip so that a transverse dimension of one salient lying intermediate its tip and the transverse center line is materially less than the aligned transverse dimension of the adjacent salient whereby an unbalanced condition is established between the magnetic forces of the arc current in adjacent salients, said magnetic unbalance causing the arc portions at opposite sides of said lesser transverse dimension to be forcibly urged in opposite directions against the insulating walls o! the chute passage tor materially cooling the arc stream.

3. Electric arc extinguishing apparatus comprising an insulating arc chute into which the interrupting arc is directed having side walls disposed in closeiy spaced relation so as to form a narrow arc space, said walls on the sides facing each other having projecting therefrom ridges extending generaly throughout said chute in the direction of arc movement, the ridges or one wall being spaced in interlocking position with respect to the ridges of the other wall so as to form a restricted tortuous arc extinguishing passage of serpentine cross section defined by alternating salients, said ridges being comparatively narrow near the base joining the corresponding chute wall and increasing in width toward the ends thereof to form interlocking portions with the ridges on the opposite chute wall thereby defining alternating salients of bulbous form whereby dissynmetry is established between the magnetic forces oi' the arc current, said dissymmetry causing the arc portions at opposite sides of the narrow section of each ridge to be forced in opposite directions against the adjacent interlocking ridges in heat transfer relation thereto.

4. Electric arc extinguishing apparatus comprising an insulating arc chute into which the intcrrupting arc is directed having side walls disposed in closely spaced relation so as to form a narrow arc space, said walls on the sides racing each other having projecting therefrom ridges extending generaliy throughout said chute in the direction of arc movement, ridges of one wall bein spaced in interleaving position with respect to ridges of the other wall to form a restricted tortuous arc extinguishing passage defined by salient extending in opposite directions, the cross sectionai thickness of individual interleaving ridges being non-uniform whereby an unbalanced condition is established between the magnetic forces of the arc current at opposite sides of a salient. said unbalanced condition causing the arc portions at opposite sides of individual interleaving ridges to be forced by reacting magnetic forces against the side walls of adjacent ridges in heat transfer relaticn thereto.

5. Electric arc extinguishing apparatus comprising an insulating arc chute into which the interrupting arc is directed having side walls disposed in closely spaced reiation so as to form a narrow arc space. said walls On the sides facing each other having projecting therefrom ridges extending generally in the direction o! arc movement, ridges ot one wall being shaped with respect to ridges of the opposite wall so that ridges of both walls are both interleaved and interlocked with respect to each other, said interlocked ridges being arranged in sufliciently spaced reiation to form a restricted tortuous arc extinguishing passage of serpentine form as viewed in cross section transverse with respect to said arc movement.

EUGENE W. BOEHNE. 

